In a recent post to his blog, Brian Teeman asks the question "is it time for an international Joomla event?" (speaking specifically of an all-Europe focused event).

Whilst I was traveling home from Joomla!Day Germany I started thinking about how long it was taking me and was the journey worthwhile. The answer was "not that long" and "yes definitely". [...] If we had a venue for Joomla!Day in the centre of Europe, in a place with excellent road, rail and air links is there any reason not to have a pan-European Joomla event.

He touches on some of the main topics involved in putting on a conference like that - the goals of the event, language differences, how long it would last, the organization of it and a few suggestions for ideal locations. It seems there's plenty of support in the comments, including a few mentions of similar events already in the works.